Pyrolysis reactions produce a complex and variable mixture of chemicals and include vaporous compounds which are normally liquid at room temperature. Pyrolysis is a general term for the thermal decomposition of any organic material (i.e. wood, plants, fossil fuels etc.) and can occur during a combustion process or in the absence of combustion. In the former, the oxidation or burning of a portion of the organic material provides the heat required to vaporize and decompose the remainder. In the absence of combustion, heat must be supplied indirectly from some other source (i.e. radiation, a solid or gaseous heat carrier, or conduction through reactor walls, etc.).
Pyrolysis of organic material or biomass produces liquids (condensable vapors), gases (non-condensables vapors) and solids (char and ash) in varying proportions depending upon reaction conditions. The pyrolysis liquids can be further subdivided into water-soluble condensable vapors and water insoluble components. It is known that the desirable active ingredients for smoke flavoring are among the water-soluble condensable vapors (liquids).
Use of pyrolysis liquid solutions as a replacement for smoking foodstuffs by direct contact with smoke produced from burning wood has become a standard industry practice. When applied to the surface of meats and other proteinaceous foodstuffs, common pyrolysis solutions not only give the foodstuff a characteristic smoke flavor, but react with the proteins to produce a coloring typical of smoked foodstuffs.
One such commercial liquid smoke preparation is the aqueous liquid smoke flavoring described by Hollenbeck in U.S. Pat. No. 3,106,473. This flavoring product is produced by slow pyrolysis or partial combustion of wood with limited access to air, followed by subsequent solvation of the desirable smoke constituents into water. The water-soluble condensable vapors are used for smoke flavor, while a water-insoluble phase which contains tar, polymers, polycyclic aromatic hydrocarbons including benzo(a)pyrene, waxes and other undesirable products unsuitable for use in food applications is discarded.
Another method of producing liquid solutions for smoke flavoring foods is the fast pyrolysis of wood or cellulose process which is disclosed by Underwood et al. in U.S. Pat. No. 4,876,108. The liquids produced by the fast pyrolysis process are collected and diluted with water to achieve a partial phase separation and to provide an aqueous liquid smoke flavored solution.
Regardless of whether wood or cellulose is pyrolyzed by a slow pyrolysis method or by a fast pyrolysis method the resulting smoke flavored liquid solutions may have a stronger smoke flavoring for some foodstuffs for a given degree of smoke coloring than is desirable for the tastes of some consumers. Even though some consumers prefer a very mild to little smoke flavor, there is still a preference that the flavored foodstuff, especially meat, have the typical full brown color associated with well smoked foodstuffs. Even though a need for such a smoke flavored liquid solution exists none seems to be presently available.